Perturbing air cooled condenser fin

ABSTRACT

An air cooled condenser fin comprises flow channel walls defining an air flow channel. The flow channel walls include planar sections separated by intermittent flow interruptions which are spaced apart along the air flow channel. The intermittent flow interruptions are defined by the flow channel walls. The intermittent flow interruptions may for example comprise splits formed by a staggered arrangement in which the planar sections of the flow channel walls before and after each split are staggered; or intermittent sinusoidal waves formed into the flow channel walls; or louvers formed into the flow channel walls to create openings passing through the flow channel walls at the louvers. The intermittent flow interruptions may be spaced apart along the air flow channel by at least 5 hydraulic diameters, and in some embodiments by 5-10 hydraulic diameters. A plurality of such air cooled condenser fins are suitably employed with the air flow channels arranged in parallel.

This application claims the benefit of U.S. Provisional Application No.62/835,706 filed Apr. 18, 2019. U.S. Provisional Application No.62/835,706 filed Apr. 18, 2019 is incorporated herein by reference inits entirety.

BACKGROUND

The following relates to air cooled condensers, heat exchanger fins andarrays thereof for air cooled condensers, and so forth.

Traditional heat exchange fins are of the straight or plain variety.Heat transfer occurs through a fin channel wherein air enters in thechannel and establishes a fluid boundary layer. Heat transfer normalizesonce the fluid boundary layer is established. Some straight fins mayhave blemishes or other features on their surface as a result ofmanufacturing processes. As such traditional fin designs may not beentirely straight nor uniform from fin to fin within a fin array.

A known modification of the straight fin design is to includeperforations in the fins to disturb air flow with the flow channel, i.e.pressed or cut perforations. They offer cross channel flow paths and arecommonly used in automotive applications. The perforations, whileeffective at disturbing the fluid boundary layer increasing heattransfer, can be impractical in certain applications as they increasethe pressure drop of the air flow.

Another known fin design employs offset fins. In this design thestraight path is cyclically offset within a channel to disturb theboundary layer. This design, as with the perforations, increase heattransfer capability but in doing so also increases pressure drop.

Another known fin design employs wavy or ruffled fins. In this designthe straight fins are curved to form sinusoidal waves. The periodicwaves enables disruption of the fluid boundary layer. Haushalter, U.S.Pat. No. 5,209,289 issued May 11, 1993, discloses a modified fin arrayincorporating wavy offsets in a unique combination.

Bugler et al., U.S. Publication No. 2018/0023901 A1 published Jan. 25,2018, discloses a heat exchange tube fin design in which a plurality ofarrowhead shapes are pressed into or embossed onto each fin. The pressedarrowhead shapes are grouped into nested pairs, and one of thearrowheads in a pair is pressed as a positive relative to the fin planeand the other of the pair is pressed as a negative relative to the finplane. The arrowhead pairs are placed in rows parallel to the air flowdirection and arrowhead pairs in one row are preferably staggeredrelative to the arrowhead pairs in the adjacent row along the fin in theair flow direction.

BRIEF SUMMARY

In some aspects disclosed herein, an air cooled condenser fin comprisesflow channel walls defining an air flow channel. The flow channel wallsinclude planar sections separated by intermittent flow interruptionswhich are spaced apart along the air flow channel. The intermittent flowinterruptions are defined by the flow channel walls.

In some illustrative embodiments, the intermittent flow interruptionscomprise splits formed by a staggered arrangement in which the planarsections of the flow channel walls before and after each split arestaggered. In some embodiments, the staggering of the flow channel wallsafter each split is about one-half of a width of the air flow channel.

In some illustrative embodiments, the intermittent flow interruptionscomprise intermittent sinusoidal waves formed into the flow channelwalls.

In some illustrative embodiments, the intermittent flow interruptionscomprise louvers formed into the flow channel walls to create openingspassing through the flow channel walls at the louvers. In someembodiments, the louvers are angled between 1 degree and 30 degrees toan air flow direction of the air flow channel. In some embodiments, theflow channel walls are secured to a tube of an air cooled condenser.

In any of the foregoing embodiments, the intermittent flow interruptionsare in some more specific embodiments spaced between 5 hydraulicdiameters and 10 hydraulic diameters apart along the air flow channel.

In any of the foregoing embodiments, the intermittent flow interruptionsare in some more specific embodiments spaced apart along the air flowchannel by at least 5 hydraulic diameters.

In some aspects disclosed herein, a plurality of air cooled condenserfins as set forth in any of the preceding paragraphs is provided, inwhich the air flow channels of the air cooled condenser fins arearranged in parallel.

In some aspects disclosed herein, an air cooled condenser comprisessteam/condensate tubes and fins attached to the steam/condensate tubes.The fins comprise flow channel walls defining parallel air flowchannels. The flow channel walls include planar sections separated byintermittent flow interruptions which are spaced apart along the airflow channels. The intermittent flow interruptions are defined by theflow channel walls. The intermittent flow interruptions in someembodiments comprise splits formed by a staggered arrangement in whichthe planar sections of the flow channel walls before and after eachsplit are staggered. The staggering of the flow channel walls after eachsplit is, in some more specific embodiments, about one-half of a widthof the air flow channel. The intermittent flow interruptions in someembodiments comprise intermittent sinusoidal waves formed into the flowchannel walls. The intermittent flow interruptions in some embodimentscomprise louvers formed into the flow channel walls to create openingspassing through the flow channel walls at the louvers. The louvers are,in some more specific embodiments, angled between 1 degree and 30degrees to an air flow direction of the air flow channel. In any of theforegoing embodiments of this paragraph, the intermittent flowinterruptions may in some more specific embodiments be spaced between 5hydraulic diameters and 10 hydraulic diameters apart along the air flowchannel. In any of the foregoing embodiments of this paragraph, theintermittent flow interruptions may in some more specific embodiments bespaced apart along the air flow channel by at least 5 hydraulicdiameters.

Some embodiments of an air cooled condenser as set forth in theimmediately preceding paragraph further comprise distribution headersconnected to feed steam into the steam/condensate tubes, and an airmoving system comprising a fan arranged to drive an airflow across thefins attached to the steam/condensate tubes. Some more specificembodiments further include risers connected to feed the steam into thedistribution headers, wherein the steam/condensate tubes, thedistribution headers, the risers, and the air moving system are arrangedto form the air cooled condenser as an A-frame type air cooled condenseror other types.

In some aspects disclosed herein, a method of cooling using an aircooled condenser fin is disclosed. The method comprises flowing airthrough an air flow channel defined by flow channel walls, andinterrupting the flowing of air at intermittent flow interruptionsdefined by the flow channel walls which are spaced apart along the airflow channel. In some more specific embodiments, the intermittent flowinterruptions are placed at locations where a boundary layer of theflowing air has normalized. In some more specific embodiments, theintermittent flow interruptions are spaced apart along the air flowchannel by at least 5 hydraulic diameters.

These and other non-limiting aspects and/or objects of the disclosureare more particularly described below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take form in various components and arrangements ofcomponents, and in various process operations and arrangements ofprocess operations. The drawings are only for purposes of illustratingpreferred embodiments and are not to be construed as limiting theinvention. This disclosure includes the following drawings.

FIG. 1 diagrammatically shows differential temperature versus length fora planar fin.

FIG. 2 diagrammatically shows heat transfer coefficient versus lengthfor a planar fin.

FIG. 3 diagrammatically shows incremental air pressure drop versuslength for a planar fin.

FIG. 4 diagrammatically shows a perspective view of a portion of an aircooled condenser fin having a single split-fin.

FIG. 5 diagrammatically shows a top view of a portion of an air cooledcondenser fin array including a plurality of splits of the type shown inFIG. 4.

FIG. 6 diagrammatically shows a perspective view air flow velocity mapfor the split fin air flow.

FIG. 7 diagrammatically shows a perspective view of a portion of an aircooled condenser fin having intermittent sinusoidal waves.

FIG. 8 diagrammatically shows a perspective view of a portion of an aircooled condenser fin having louvers.

FIG. 9 diagrammatically shows a top view of a portion of an air cooledcondenser fin array including a plurality of louvers of the type shownin FIG. 8.

FIG. 10 plots heat transfer coefficient of an air cooled condenser finwith splits, versus position.

FIG. 11 plots heat transfer coefficient of an air cooled condenser finwith intermittent sinusoidal waves, versus position.

FIG. 12 diagrammatically shows a typical air cooled condenserapplication of the disclosed improved fins, where the illustrative aircooled condenser is of the forced draft A-frame type.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For certain applications, such as air-cooled condensers, excessivepressure drop creates design constraints when applying fins to a tubegeometry. A need exists for new and improved fin and fin array designsthat minimize heat exchanger footprint opposite need for additionalpower input needed to move air/overcome excessive pressure drops ofexisting designs.

Air-cooled condenser applications have some requirements regarding thesteam flow area and resultant pressure drop that places constraints onthe minimum sizing of the heat exchanger fin tube base. Use of existingnon-planar fin designs (Louvered, Offset, Wavy, etc.) requiresadditional power input (larger air mover sizing) to apply the fin to therequired tube geometry. Further, redesigning tube geometry toincorporate a non-planar fin design in a lower power input design isoften uneconomical.

Flow on the air-side of an air-cooled condenser generally operates inthe laminar regime, which is defined by Reynolds numbers less than 2000.In this regime, momentum and energy transport occur via the mechanism ofmolecular diffusion, which is driven by gradients in the velocityprofile. The velocity gradients near the fin wall are especiallyimportant in determining the momentum and energy transport rates in thelocal region as the air flows through the fin channel. As the air in thefree-stream approach region enters the fin channels, extremely highvelocity gradients result, based on the large velocity differentialbetween the entering air velocity and the zero-velocity condition at thefin wall. This results in large friction factors and heat transfercoefficients at the lead edge of the fin. As the flow progresses downthe fin channel, the velocity profile approaches the fully developedprofile (generally parabolic). As this transition occurs, the localvelocity gradients at the fin wall are reduced, and the local frictionfactor and heat transfer coefficient values gradually approach the fullydeveloped values. This transition often occurs within ten (10) hydraulicdiameters from the entrance to the fin section. The hydraulic diameter,D_(H), is a commonly used term when handling flow in non-circular tubesand channels, and is defined as

$\begin{matrix}{D_{H} = \frac{4A}{P}} & (1)\end{matrix}$

where A is the cross-sectional area of the flow and P is the wettedperimeter of the cross-section (where the wetted perimeter includes allsurfaces acted upon by shear stress from the fluid). For a closedrectangular channel of dimensions a×b, the hydraulic diameter D_(H) isgiven by:

$\begin{matrix}{D_{H,{rect}} = {\frac{4A}{P} = {\frac{4\left( {a \times b} \right)}{a + b + a + b} = \frac{2ab}{a + b}}}} & (2)\end{matrix}$

The entrance region of the fin is therefore more effective in terms ofheat transfer than the remainder of the fin, although the increase inheat transfer comes at the cost of added pressure drop.

With reference to FIGS. 1-3, numerical simulations of differentialtemperature versus length (FIG. 1), heat transfer coefficient versuslength (FIG. 2), and incremental air pressure drop versus length (FIG.3) are shown for a planar fin. In FIGS. 1, 2, and 3, the entrance regionis to the left, with the air flow proceeding along the channel of lengthL to the exit side of the fin on the right of the curve. The mosteffective region of heat transfer in a planar fin of an air cooledcondenser is at the air entrance into the fin channel. This is evidentin FIG. 2 where the heat transfer coefficient decreases rapidly as airflows along the channel length.

FIG. 4 is a graphic representation showing a single split-fin 10 asdisclosed herein. The split-fin takes advantage of the enhanced heattransfer which occurs at the lead edge of a fin channel entrance toreduce the total surface area of the overall fin assembly. The split-finarrangement of FIG. 4 comprises a straight fin section 12 having a finchannel 14 that is subsequently split into two fin channels 16, 18 at asplit point 20 along the length of the fin channel 14. The split 20preferably occurs at or around the point where air flow has fullydeveloped in the first channel section 14. As air flow (indicated byarrows F in FIG. 4) enters the staggered fin arrangement 20, it is splitinto subsequent sections, i.e. split air flows 16, 18. The fin wall ofthe downstream fin section 22 is located at or near the center of theupstream flow path or channel 14 (in other words, the staggering of thefin walls after the split is about one-half of a width of the air flowchannel), thereby being exposed to high velocity gradients near thewall, similar to what occurs at the entrance of the first fin section12. This process is repeated at each flow split, resulting in increasedheat transfer at the lead edge region of every fin section 12, 22. Amore compact fin assembly configuration results; requiring less finsurface area and comparatively less material needed to construct the finarray than traditional designs.

With reference to FIG. 5, when the split-fin is formed into a fin array,each flow split results in increased heat transfer coefficient andfriction factor in the local region near the respective fin sectionentrance. FIG. 5 illustrates a fin array including successiveillustrated fin sections 12 a, 12 b, 12 c with respective channels 14 a,14 b, 14 c, with fin split point 20 ab at the junction of fin sections12 a, 12 b and fin split point 20 bc at the junction of fin sections 12b, 12 c. This is repeated for as many fin split sections exist in theassembly. The local increases in friction factor result in an increasein pressure drop, which is generally undesirable. Heat transfer from thefin to the air depends on two factors, the local heat transfercoefficient, and the local bulk air-to-fin temperature difference. Theflow splits 20 increase the local heat transfer coefficient, which isbeneficial. As with friction factor, the local increase in heat transfercoefficient resulting from each flow split 20 is consistent throughoutthe fin assembly. However, as the air flow F proceeds through theassembly, the temperature difference between the air and the fin iscontinuously reduced. Therefore, the effectiveness of the flow splits 20with respect to increased local heat transfer decreases the farther theparticular flow split is from the fin assembly entrance. For thisreason, it is beneficial to cluster the flow splits 20 near the entranceto the assembly and use a more continuous section at the trail end of afin assembly comprising multiple split-fins.

With reference to FIG. 6, in another embodiment, an air cooled condenserutilizes single row finned tubes and includes a split-feature within theair flow channel which disturbs the boundary layer along the flowchannel wall. FIG. 6 shows a perspective view air flow velocity map forthe split fin air flow.

The concepts of split-fins is not intended to be limited by thepreceding discussion. Split features may be repeating or intermediate.Flow channel walls may be discontinuous or continuous. Flow along thewall of a planar fin may be perturbed by the channel being cut, and anew channel formed with the opening offset from the outlet of theoriginal channel. Fin channels may consist of single or multiple splits.

Channel length of the fin sections 12 is preferably determined byfinding the point along the wall in which the air flow boundary layerapproaches fully developed profile. In one embodiment having multiplesplits the splits are spaced between about 5 hydraulic diameters andabout 10 hydraulic diameters apart.

With reference to FIG. 7, in an alternative embodiment one or more finchannels in the fin array may include intermittent sinusoidal waves. Agraphic representation of a fin 30 having a channel 34 with anintermittent sinusoidal wave 32 is shown in FIG. 7. Flow F along thewall of the channel 34 is redirected by the sinusoidal wave 32 in thetransverse direction of air flow F. Wave geometry of the sinusoidal wave32 is designed to optimize full channel recirculation downstream fromthe disturbance. Planar fin wall is placed between the multiple waves 32until boundary layer normalizes to reduce pressure drop. The sinusoidalwaves 32 are preferably spaced between about 5 hydraulic diameters andabout 10 hydraulic diameters apart.

With reference to FIGS. 8 and 9, in yet another embodiment, louveredfins 40 are disclosed. In this embodiment, openings 42 between adjacentfin channels 44 are used. Openings may take the form of louvers 46angled between about 1 and about 30 degrees to the direction of flow.FIGS. 8 and 9 provide graphic representations of the openings 42 betweenadjacent fin channels 44. As seen in FIG. 8, the openings 42 do notcomprise the entirely of the flow channel wall. While FIGS. 8 and 9 showalignment between openings in adjacent channels, such alignment is notpresent in some embodiments; rather, in these embodiments the openingmay alternatively be offset. FIG. 8 also illustrates the louvered fins40 soldered (or otherwise attached) to a tube 48 as is common in thecase of an air cooled condenser (where the steam or other fluid beingcondensed flows through the tube 48). It is noted that FIGS. 8 and 9show the louvers in the “pointing downstream” configuration. In thisconfiguration the tips of the louvers are pointing roughly in thedirection of the flow from upstream to downstream. In a variantembodiment, the louvers may be reversed, so as to point “into” the flowin the upstream direction. Either configuration can be employedeffectively.

The innovations disclosed herein may be used on a single channel, acombination of channels, and/or combined with one another to form newand unique fin arrays that improve heat transfer over a variety of tubegeometries that may be subject to space constraints and otherwise havelimitations on ability to overcome pressure drop concerns. Furtheradvantageous is the reduction in materials requirements for fin arraysenabled by the approaches disclosed herein.

FIGS. 10 and 11 plots show simulated data relating to heat transfercoefficient of the split-fin and intermittent wave, respectively,against position. As shown in these figures, the heat transfer peaks atthe location of the flow interruption and decreases along the length ofthe channel as the boundary layer is reestablished and the difference intemperature between the two fluids, air and steam, is gradually reduced.

With reference now to FIG. 12, a typical air cooled condenserapplication of the disclosed improved fins is shown. An illustrative aircooled condenser shown in FIG. 12 is of the forced draft A-frame type.An electric power generator 52 is driven by a steam turbine 54 usingsteam 56. Exhaust steam 58 discharged from the steam turbine 54 flowsinto a main steam duct 60 and a distribution manifold 62, thatdistributes the steam to a set of air cooled condensers, an illustrativeone of which is shown in FIG. 12. The steam flows up through risers 64which are connected to feed the steam into distribution headers 66 whichin turn are connected to feed the steam into bundles 70 that includesteam/condensate tubes (e.g., the illustrative steam/condensate tube 48shown in FIG. 8) with fins (such as split fins 10 as shown in FIGS. 4-6;or fins 30 with intermittent sinusoidal waves 32 as shown in FIG. 7; orfins 40 with louvers 46 as shown in FIGS. 8 and 9) soldered or otherwiseattached to the steam/condensate tubes. An air moving system 72, such asa fan, drives an airflow across the fins of the bundles 70 in order tocool and condense the steam in the tubes to form condensate. FIG. 12further shows the condenser superstructure including a fan deck 74supported by support structure 76 and bracing 78, and a windwallstructure 80 atop the fan deck 74. While the illustrative air cooledcondenser is of the forced draft A-frame type, the disclosed improvedfins are suitably employed in conjunction with air cooled condensers ofother types, such as an induced draft V-frame condenser type, a flatcondenser type, or so forth.

The inventors have performed computer simulations of the performance ofvarious designs of split fins 10 (FIGS. 4-6), fins 30 with intermittentsinusoidal waves 32 (FIG. 7), and fins 40 with louvers 46 (FIGS. 8 and9). In these simulations, the fins were modeled as rectangular channelswith rectangular dimension H_(fin) being the fin height (that is, thedistance the fin extends away from the steam/condensate tube to which itis soldered) and dimension S_(fin) being the separation between the finwalls defining the air flow channel. Using the hydraulic diameter for arectangular channel given in Equation (2), this yields the followinghydraulic diameter D_(H,fin) for the fins:

$\begin{matrix}{D_{H,{fin}} = {\frac{4A}{P} = {\frac{2ab}{a + b} = \frac{2\left( {S_{fin} \times H_{fin}} \right)}{S_{fin} + H_{fin}}}}} & (3)\end{matrix}$

More generally, for an air flow channel of arbitrary cross sectionaldimensions the first expression of Equation (3) holds, i.e.

$D_{H,{fin}} = \frac{4A}{P}$

where A is the cross-sectional area of the air flow channel and P is theperimeter of the cross-section of the air flow channel, and with a tubebundle length “L” (also indicated as bundle length 82 if FIG. 12). Thesimulations were for a design of the bundles 70 that included 11 finsper inch. The simulations also modeled the energy (in horsepower whichis related to pressure loss across a bundle) of the air moving system(e.g. fan) 72 and the bundle tube length 82. In addition to modelingperformance of the designs of the split fins 10, fins 30 withintermittent sinusoidal waves 32, and louvered fins 40, simulations wereperformed to model the performance of conventional planar fin andcontinuous wavy fin designs. The simulations concluded that utilizingthe planar fin design with the intermittent perforations, i.e., splitfins 10, fins 30 with intermittent sinusoidal waves 32, and louveredfins 40 would enable reduction of the tube bundle length 82 byapproximately 10% with only a moderate increase of 30% in the fan energyconsumption (horsepower). The cost savings in reducing the tube bundlelength by 10% is order magnitude greater than the cost of higher energyfan. On the other hand, the bundle with the continuous wavy fin designwould reduce the tube bundle length by 16% but at the price of 700%increase in energy consumption which is prohibitive.

These simulations confirm the mechanism for improved performancedisclosed herein, namely that employing mostly planar fins but withintermittent flow interruptions positioned at points where the boundarylayer normalizes can achieve the desired heat transfer efficiencyimprovement while only imposing a modest increase in pressure drop. Itwas found that the intermittent flow interruptions are in someembodiments preferably spaced between about 5 hydraulic diameters andabout 10 hydraulic diameters apart to optimally balance heat transferefficiency (improved by the intermittent flow interruptions) againstpressure drop introduced by the interruptions. The intermittent flowinterruptions can be fin splits 20 (as in the embodiments of FIGS. 4-6),intermittent sinusoidal waves 32 (as in the embodiment of FIG. 7),louvers 46 (as in the embodiments of FIGS. 8 and 9), or more generallyany other type of intermittent interruption. The simulations also foundthat placing the intermittent flow interruptions nearer the entranceside of the fin maximizes the heat transfer benefit while imposing theleast additional pressure drop. For example, in some nonlimitingembodiments at least 70% of the intermittent flow interruptions arepositioned within the first one-half of the fin length L (that is,within the half-fin length closest to the entrance side of the fin). Insome other nonlimiting embodiments, at least 80% of the intermittentflow interruptions are positioned within the first one-third of the finlength L (that is, within the first third of the fin length that isclosest to the entrance side of the fin).

It should be noted that the term “planar fin” is used herein in itsusual and ordinary meaning in the art, as a fin that channels air flowprincipally along a single planar channel. In a planar section of a fin,the flow channel walls defining the air flow channel may have somedeviations from geometrically perfect planar form, for example due tounintended manufacturing-induced variations, dimples, wall curvature, orso forth. Such a imperfections typically do not have a meaningful impacton air flow and hence are considered “planar” fin sections as usedherein. Likewise, the term “intermittent flow interruption” as usedherein is an intentional (i.e. design-basis) modification to a fin wallor walls, or a fin split, that is sufficient to induce air flowinterruption as described herein. Hence, unintendedmanufacturing-induced variations, dimples, wall curvature, or so forthare not considered “intermittent flow interruptions” as used herein.

Illustrative embodiments including the preferred embodiments have beendescribed. While specific embodiments have been shown and described indetail to illustrate the application and principles of the invention andmethods, it will be understood that it is not intended that the presentinvention be limited thereto and that the invention may be embodiedotherwise without departing from such principles. In some embodiments ofthe invention, certain features of the invention may sometimes be usedto advantage without a corresponding use of the other features.Accordingly, all such changes and embodiments properly fall within thescope of the following claims. Obviously, modifications and alterationswill occur to others upon reading and understanding the precedingdetailed description. It is intended that the present disclosure beconstrued as including all such modifications and alterations insofar asthey come within the scope of the appended claims or the equivalentsthereof.

We claim:
 1. An air cooled condenser fin comprising: flow channel wallsdefining an air flow channel; wherein the flow channel walls includeplanar sections separated by intermittent flow interruptions which arespaced apart along the air flow channel; wherein the intermittent flowinterruptions are defined by the flow channel walls.
 2. The air cooledcondenser fin of claim 1 wherein the intermittent flow interruptionscomprise splits formed by a staggered arrangement in which the planarsections of the flow channel walls before and after each split arestaggered.
 3. The air cooled condenser fin of claim 2 wherein thestaggering of the flow channel walls after each split is about one-halfof a width of the air flow channel.
 4. The air cooled condenser fin ofclaim 2 wherein the splits are spaced between 5 hydraulic diameters and10 hydraulic diameters apart along the air flow channel.
 5. The aircooled condenser fin of claim 2 wherein the splits are spaced apartalong the air flow channel by at least 5 hydraulic diameters.
 6. The aircooled condenser fin of claim 1 wherein the intermittent flowinterruptions comprise intermittent sinusoidal waves formed into theflow channel walls.
 7. The air cooled condenser fin of claim 6 whereinthe intermittent sinusoidal waves are spaced between 5 hydraulicdiameters and 10 hydraulic diameters apart along the air flow channel.8. The air cooled condenser fin of claim 6 wherein the intermittentsinusoidal waves are spaced apart along the air flow channel by at least5 hydraulic diameters.
 9. The air cooled condenser fin of claim 1wherein the intermittent flow interruptions comprise louvers formed intothe flow channel walls to create openings passing through the flowchannel walls at the louvers.
 10. The air cooled condenser fin of claim9 wherein the louvers are angled between 1 degree and 30 degrees to anair flow direction of the air flow channel.
 11. The air cooled condenserfin of claim 9 wherein the flow channel walls are secured to a tube ofan air cooled condenser.
 12. The air cooled condenser fin of claim 9wherein the louvers are spaced between 5 hydraulic diameters and 10hydraulic diameters apart along the air flow channel.
 13. The air cooledcondenser fin of claim 9 wherein the louvers are spaced apart along theair flow channel by at least 5 hydraulic diameters.
 14. The air cooledcondenser fin of claim 1 wherein the intermittent flow interruptions arespaced between 5 hydraulic diameters and 10 hydraulic diameters apartalong the air flow channel.
 15. The air cooled condenser fin of claim 1wherein the intermittent flow interruptions are spaced apart along theair flow channel by at least 5 hydraulic diameters.
 16. An air cooledcondenser comprising a plurality of air cooled condenser fins as setforth in claim 1 wherein the air flow channels of the air cooledcondenser fins are arranged in parallel.
 17. An air cooled condensercomprising: steam/condensate tubes; fins attached to thesteam/condensate tubes; wherein the fins comprise flow channel wallsdefining parallel air flow channels, the flow channel walls includingplanar sections separated by intermittent flow interruptions which arespaced apart along the air flow channels; wherein the intermittent flowinterruptions are defined by the flow channel walls.
 18. The air cooledcondenser of claim 17 wherein the intermittent flow interruptionscomprise splits formed by a staggered arrangement in which the planarsections of the flow channel walls before and after each split arestaggered.
 19. The air cooled condenser of claim 18 wherein thestaggering of the flow channel walls after each split is about one-halfof a width of the air flow channel.
 20. The air cooled condenser ofclaim 17 wherein the intermittent flow interruptions compriseintermittent sinusoidal waves formed into the flow channel walls. 21.The air cooled condenser of claim 17 wherein the intermittent flowinterruptions comprise louvers formed into the flow channel walls tocreate openings passing through the flow channel walls at the louvers.22. The air cooled condenser of claim 21 wherein the louvers are angledbetween 1 degree and 30 degrees to an air flow direction of the air flowchannel.
 23. The air cooled condenser of claim 17 wherein theintermittent flow interruptions are spaced between 5 hydraulic diametersand 10 hydraulic diameters apart along the air flow channel.
 24. The aircooled condenser of claim 23 wherein the air flow channels arerectangular with the hydraulic diameter D_(H,fin) of each air flowchannel being:$D_{H,{fin}} = \frac{2\left( {S_{fin} \times H_{fin}} \right)}{S_{fin} + H_{fin}}$where H_(fin) is a fin height and S_(fin) is a separation between thefin walls defining each air flow channel.
 25. The air cooled condenserof claim 23 wherein the hydraulic diameter D_(H,fin) of each air flowchannel is: $D_{H,{fin}} = \frac{4A}{P}$ where A is the cross-sectionalarea of each air flow channel and P is the perimeter of thecross-section of each air flow channel.
 26. The air cooled condenser ofclaim 17 wherein the intermittent flow interruptions are spaced apartalong the air flow channel by at least 5 hydraulic diameters.
 27. Theair cooled condenser of claim 26 wherein the air flow channels arerectangular with the hydraulic diameter D_(H,fin) of each air flowchannel being:$D_{H,{fin}} = \frac{2\left( {S_{fin} \times H_{fin}} \right)}{S_{fin} + H_{fin}}$where H_(fin) is a fin height and S_(fin) is a separation between thefin walls defining each air flow channel.
 28. The air cooled condenserof claim 26 wherein the hydraulic diameter D_(H,fin) of each air flowchannel is: $D_{H,{fin}} = \frac{4A}{P}$ where A is the cross-sectionalarea of each air flow channel and P is the perimeter of thecross-section of each air flow channel.
 29. The air cooled condenser ofclaim 17 further comprising: distribution headers connected to feedsteam into the steam/condensate tubes; and an air moving systemcomprising a fan arranged to drive an airflow across the fins attachedto the steam/condensate tubes.
 30. The air cooled condenser of claim 29further comprising: risers connected to feed the steam into thedistribution headers; wherein the steam/condensate tubes, thedistribution headers, the risers, and the air moving system are arrangedto form the air cooled condenser as an A-frame type air cooledcondenser.
 31. The air cooled condenser of claim 17 wherein at least 70%of the intermittent flow interruptions are positioned within a firstone-half of a length of the fins closest to an air flow entrance offins.
 32. A method of cooling using an air cooled condenser fin, themethod comprising: flowing air through an air flow channel defined byflow channel walls; and interrupting the flowing of air at intermittentflow interruptions defined by the flow channel walls which are spacedapart along the air flow channel.
 33. The method of claim 32 wherein theintermittent flow interruptions are placed at locations where a boundarylayer of the flowing air has normalized.
 34. The method of claim 32wherein the intermittent flow interruptions are spaced apart along theair flow channel by at least 5 hydraulic diameters.